I just battled columnaris after using some driftwood. I had boiled it for a few hours first. I cant say it was carried by the driftwood, but if your going to use stuff from local water, I think I would into how to minimize risk if putting it into your tank. My $.02
Wow! is that a nymph?I agree, there are all kinds of bacteria, and other parasites (including Lernaea and predatory dragonfly larvae) that don't simply rinse off.
Making a dip for plants of aluminum sulfate or potassium permanganate can help to remove many problems.
I bring in plants from my pond in winter every year, and after a time noticed young fish disappearing in a grow out tank, wasn't easy to find the culprit in the plants.